VP DP-SM drain screw leaking

[HiWard]

I have a small leak from the drain screw after changing the gear oil a few weeks ago. I'm pretty sure I have the right o-ring (part number 955981) and I also ordered a new drain screw and set of o-rings. Same problem. Tightened screw to spec according to workshop manual. Any ideas?

I also wonder why the groove is bigger than the o-ring (image shows old my old drain screw). I tapet the treads with electrical tape before sliding on the o-ring so it should not be damaged.

 

[Scott Danforth]

that o-ring is too small for the groove

that looks like a 1.25 mm diameter o-ring jump up to a larger cross-section

 

[HiWard]

that o-ring is too small for the groove

that looks like a 1.25 mm diameter o-ring jump up to a larger cross-section

I'm inclined to agree, but it's strange since I ordered the part directly from VP based on the diagrams for my drive. Does anyone have the partnumber for a larger o-ring?

 

[Scott Danforth]

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[Scott06]

I'm inclined to agree, but it's strange since I ordered the part directly from VP based on the diagrams for my drive. Does anyone have the partnumber for a larger o-ring?

Order a fatter one or get a O ring kit from the hardware store.

VP may have the wrong O ring in their inventory. I had a similar situation at work where a OEM manufacturer used a teflon coated o-ring on a mechanical pump seal - it looked like a sausage... Of course from an OEM this was like a $40 Oring. They started sending uncoated Orings. I refused the part , eventually the parts guy got back to me that their supplier sent the wrong part to them in a bag with the correct part number...

Either way that o-ring does not look like it fits that groove.

 

[bruceb58]

I always replaced the o-ring every time I changed gear oil. The one thing you HAVE to do is cover the threads with tape before sliding the o-ring over them. The thread will damage the o-ring if you don't.

To me, the o-ring looks like the correct one. I had the exact same drive.

 

[HiWard]

I always replaced the o-ring every time I changed gear oil. The one thing you HAVE to do is cover the threads with tape before sliding the o-ring over them. The thread will damage the o-ring if you don't.

To me, the o-ring looks like the correct one. I had the exact same drive.

I did that after reading about it online somewhere. It’s a good tip.

 

[Horigan]

I would find one with a thicker cross section. Volvo O-ring call outs aren't always perfect. I recently lost a Volvo TAMD41P diesel engine due in part to an incorrect Volvo call out for the dip stick O-ring size.

Checkout their call out, right, verses what I tried, but was too tight, middle, to the perfect one I found after toasting the engine, left.

 

[HiWard]

I would find one with a thicker cross section. Volvo O-ring call outs aren't always perfect. I recently lost a Volvo TAMD41P diesel engine due in part to an incorrect Volvo call out for the dip stick O-ring size.

Checkout their call out, right, verses what I tried, but was too tight, middle, to the perfect one I found after toasting the engine, left.
View attachment 391907

Sorry to hear about your engine. I measured the thickness of the o-ring at 1.6mm (w) and the ID at 7.1mm (pardon my metric). The drain screw diameter is 8.11mm in the groove.

 

[Scott Danforth]

Get same OD with a 2mm cross section

 

[HiWard]

Get same OD with a 2mm cross section

I will drain the lower unit and check the drain hole for debris and replace the o-ring with a 2mm cross section if if looks good.

 

[Horigan]

One thing I would caution when going with a thicker cross section is to only go slightly bigger. Otherwise you risk the O-ring smearing out of the groove and not creating a seal. That's what happened with my diesel dip stick O-ring. The middle one above was a little tough to get into the dipstick and over time started to smear out of the groove with repeated insertions. The one on the left looks almost the same, but goes into the dipstick much more easily.

 

[HiWard]

I’ve replaced the o-ring again, poked around the drain hole before reinserting the plug. Will leave it overnight and see if it holds.

 

[Fun Times]

I’ve replaced the o-ring again, poked around the drain hole before reinserting the plug. Will leave it overnight and see if it holds.

Have you checked closely the carrier housing area where the screw goes into for damage such as a crack, corrosion, etc..?

Item number 12,

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[HiWard]

Have you checked closely the carrier housing area where the screw goes into for damage such as a crack, corrosion, etc..?

Item number 12,

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No, I haven’t, that would be the worst case scenario I imagine. Is the carrier housing made from steel or aluminium?

 

[bruceb58]

And make sure it's actually leaking from the drain plug. Few ways oil can leak in that area.

May even be wise to pressure test with that plug in place. Spray soapy water around until you see where it's actually leaking.

 

[Fun Times]

No, I haven’t, that would be the worst case scenario I imagine. Is the carrier housing made from steel or aluminium?

Depending on inspection done thus far for a screw to O-ring issue, I’d be more inclined to think there’d be an issue with either the bearing housing O-ring to the lower unit case housing or more common of an issue sometimes depending on water usage boats used in, would be corrosion damage between both housings as that bearing carrier is changed out somewhat often due to corrosion damage or other.

As mentioned, it’s time for a pressure test.

 

[HiWard]

As mentioned, it’s time for a pressure test.

I guess it is. Never done it before, is there a good DIY way of performing a pressure test?

 

[Fun Times]

See if these videos will help guide you some,

PS: you can test with this drive model still on the boat which helps.

 

[bruceb58]

I own one of these

Gearcase Pressure Tester | Stevens Instrument Company

www.stevensinstrument.com

Looks like the same one used in that video.

I also own their vacuum tester